A gear grinding machine has been conventionally provided as a machine which grinds a thermally treated gear by using a threaded grinding wheel or the like to efficiently finish the tooth surfaces of the gear. In such a gear grinding machine, the gear is ground by rotating the threaded grinding wheel and the gear relative to each other with the threaded grinding wheel and the gear meshed with each other. Hence, before the threaded grinding wheel and the gear are meshed with each other to grind the gear, a tooth alignment operation is performed in which edges (crests and troughs) of the threaded grinding wheel and teeth (crests and troughs) of the gear establish a meshable rotational phase relationship.
Moreover, among the gear grinding machines, a gear grinding machine as follows is provided. In order to reduce a processing cycle time, the gear grinding machine controls the rotational phase of a gear to complete the tooth alignment operation described above, before the gear is conveyed to a workpiece processing position. Such a gear grinding device configured to perform the tooth alignment operation is disclosed, for example, in Patent Document 1.